Summary of Significant Accounting Policies - Calculation of Basic and Diluted EPS (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	May 31, 2013	May 31, 2012	May 31, 2011
Earnings
Net income (loss) from continuing operations	$ (10,494)	$ 1,928	$ (69,472)
Net income from discontinued operations	35,044	5,548	4,559
Unvested restricted share and unit participation	0	(3)	31
Income (loss) allocated to common shareholders	$ 24,550	$ 7,473	$ (64,882)
Shares
Weighted-average shares outstanding (in shares)	28,175	27,927	27,836
Contingently issuable shares (in shares)	4	2	2
Unvested restricted shares (in shares)	(16)	(15)	(13)
Basic weighted-average shares (in shares)	28,163	27,914	27,825
Stock option, restricted share and award dilution (in shares)	0	102	0
Diluted weighted-average shares (1) (in shares)	28,163	28,016	27,825
NET INCOME (LOSS) PER SHARE FROM CONTINUING OPERATIONS:
Basic (in USD per share)	$ (0.37)	$ 0.07	$ (2.49)
Diluted (in USD per share)	$ (0.37)	$ 0.07	$ (2.49)
NET INCOME FROM DISCONTINUED OPERATIONS:
Basic (in USD per share)	$ 1.24	$ 0.20	$ 0.16
Diluted (in USD per share)	$ 1.24	$ 0.20	$ 0.16
NET INCOME (LOSS) PER SHARE:
Basic (in USD per share)	$ 0.87	$ 0.27	$ (2.33)
Diluted (in USD per share)	$ 0.87	$ 0.27	$ (2.33)
Shares excluded due to antidilutive effect of stock options, restricted shares and awards (in shares)	807	1,280	1,032